设置α通道，更新imageview视图

import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.widget.ImageView;import android.widget.TextView;public class Activity01 extends Activity{//声明ImageView对象ImageViewimageview;TextViewtextview;//ImageView的alpha值，intimage_alpha= 255;HandlermHandler= new Handler();//控件线程booleanisrung= false;/** Called when the activity is first created. */@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);isrung= true;//获得ImageView的对象imageview = (ImageView) this.findViewById(R.id.ImageView01);textview = (TextView) this.findViewById(R.id.TextView01);//设置imageview的图片资源。同样可以再xml布局中像下面这样写//android:src="@drawable/logo"imageview.setImageResource(R.drawable.logo);//设置imageview的Alpha值imageview.setAlpha(image_alpha);//开启一个线程来让Alpha值递减new Thread(new Runnable() {public void run(){while (isrung){try{Thread.sleep(200);//更新Alpha值updateAlpha();}catch (InterruptedException e){e.printStackTrace();}}}}).start();//接受消息之后更新imageview视图mHandler = new Handler() {@Overridepublic void handleMessage(Message msg){super.handleMessage(msg);imageview.setAlpha(image_alpha);textview.setText("现在alpha值是："+Integer.toString(image_alpha));//更新imageview.invalidate();}};}public void updateAlpha(){if (image_alpha - 7 >= 0){image_alpha -= 7;}else{image_alpha = 255;//isrung = false;}//发送需要更新imageview视图的消息mHandler.sendMessage(mHandler.obtainMessage());}}